The field of the invention is dough sheeter machines.
Dough sheeter machines are used to produce relatively thin sheets of dough, to make food products such as tortillas and chips. For these types of products, masa is made from wet milled corn, i.e., corn flour, water and other ingredients. The dough is rolled into a thin sheet by pressing and rolling the dough between rollers. A cutting or die roller is pressed against a front roller, to cut out the selected shape for the product. For example, tortillas are cut in a round shape, whereas chips may be cut in triangular shapes. After cutting, the food product is generally toasted, baked or fried, and then packaged. While sheeters or dough sheeting machines are most often used with masa, they may also be used with other food products, such as doughs made from rice, wheat, etc.
While the physical properties of doughs vary among batches of masa or other food products, most doughs have certain adhesive qualities which tend to cause the dough to stick to the rollers of sheeting machines. After the food product is cut into the desired shape by the die roller, the cut shapes must be separated from the front roller and conveyed from the sheeting machine to a subsequent (for example, a baking) station for further processing. The web remaining on the front roller after cutting makes up a significant fraction of the dough fed into the machine. Consequently, for economical operation, the web must be returned for refeeding into the sheeter machine.
Various techniques have been proposed for separating the cut food product shapes from the front roller, and for returning the web to the supply of dough being fed into the sheeter machine. These techniques include use of stripper wires, concave rollers, doctor blades and varying roller speeds. Stripper wires, i.e., wires tensioned across the front roller, are widely used. Bands have also been used in sheeter machines to help return the web back into the sheeter machine. Yet significant difficulties remain in the design and operation of sheeter machines.
Most sheeter machines have used a roughened or sandblasted front roller and a smooth, e.g., Teflon coated rear roller. The rough surface on the front roller has been required to pull the dough down into the space or gap between the front and rear rollers. Without this rough surface, the dough slips excessively and does not reliably feed into the gap. This causes air pockets or voids in the food product. Unfortunately, while the rough front roller surface reduces or avoids air pockets, it also places high loads on the stripper wires, as the food product sticks tightly to the rough surface. The stripper wires have to cut or shear through the food products or tortillas, leaving them with a rough surface. As a result, the stripper wires wear out frequently and must be replaced. This requires the sheeter machine to be shut down. If the dough is allowed to dry on the rough front roller, removing it can become very difficult. The length of the stripper wires, and hence the length of the front roller is also severely limited due to the high loads placed on the stripping wires in shearing through the dough. This limit on the length of the roller limits the manufacturing capacity of the machine.
In addition, using these known designs causes the quality of the food product to suffer, because the rough surface of the wire stripped food product looses excessive moisture in subsequent baking or toasting operations. The end product has less retained moisture, and a rough surface. These are undesirable characteristics, especially for tortillas.